The protein oxalate oxidase catalyzes the following reaction:

(COOH)2 + O2 = 2 CO2 + H2O2

Oxalate oxidase may have various roles in the cell. Since plants store calcium ions as calcium oxalate, oxalate oxidase may allow plants to access calcium ions during periods of stress or senescence. Influxes of calcium ions may also help sustain the oxidative burst of hydrogen peroxide related to the hypersensitive response and lignification. The hydrogen peroxide produced from this reaction could also be involved in strengthening the cell wall and is toxic to microorganisms. The overexpression of the protein may also promote salicylic acid synthesis and induction of signaling cascades involved in plant defense. Transgenic applications of the protein confer tolerance to fungal pathogens reliant on oxalic acid secretion. The enzyme also appears to be involved during wheat embryo development as the protein is glycosylated to the cell wall to provide hydrogen peroxide for cross-linking reactions during cell wall expansion and lignification.